1. Field of the Invention
This invention relates to a method for using an orally administered sustained release ranolazine dosage formulations to maintain human ranolazine plasma levels at therapeutic levels.
2. Description of the Art
U.S. Pat. No. 4,567,264, the specification of which is incorporated herein by reference, discloses ranolazine, (±)—N—(2,6-dimethylphenyl)-4-[2-hydroxy-3-(2-methoxyphenoxy)-propyl]-1-piperazineacetamide, and its pharmaceutically acceptable salts, and their use in the treatment of cardiovascular diseases, including arrhythmias, variant and exercise-induced angina, and myocardial infarction.
U.S. Pat. No. 5,506,229, which is incorporated herein by reference, discloses the use of ranolazine and its pharmaceutically acceptable salts and esters for the treatment of tissues experiencing a physical or chemical insult, including cardioplegia, hypoxic or reperfusion injury to cardiac or skeletal muscle or brain tissue, and for use in transplants. Conventional oral and parenteral formulations are disclosed, including controlled release formulations. In particular, Example 7D of U.S. Pat. No. 5,506,229 describes a controlled release formulation in capsule form comprising microspheres of ranolazine and microcrystalline cellulose coated with release controlling polymers.
The presently preferred route of administration for ranolazine and its pharmaceutically acceptable salts and esters is oral. A typical oral dosage form is a compressed tablet, a hard gelatin capsule filled with a powder mix or granulate, or a soft gelatin capsule (softgel) filled with a solution or suspension. U.S. Pat. No. 5,472,707, the specification of which is incorporated herein by reference, discloses a high-dose oral formulation employing supercooled liquid ranolazine as a fill solution for a hard gelatin capsule or softgel.
As set forth in application Example 3, the initial trials of ranolazine on humans suffering from angina were failures. The trials used an immediate release of ranolazine formulation at a dose level of 120 mg taken three times daily. Based upon the initial experiments, it was uncertain whether or not ranolazine could be given to humans in an amount and mode that is effective against angina.
One problem with conventional oral dosage formulations is that they are not ideally suited to ranolazine and its pharmaceutically acceptable salts, because the solubility of ranolazine is relatively high at the low pH that occurs in the stomach. Furthermore ranolazine also has a relatively short plasma half-life. The high acid solubility property of ranolazine results in rapid drug absorption and clearance, causing large and undesirable fluctuations in plasma concentration of ranolazine and a short duration of action, thus necessitating frequent oral administration for adequate treatment.
There is therefore a need for a method for administering ranolazine in an oral dosage form once or twice daily that provides therapeutically effective plasma concentrations of ranolazine for the treatment of angina in humans.